1. Field of Invention
The invention relates to a cable, more particularly to a coaxial cable which has a sound electromagnet shielding to prevent interference from outside said coaxial cable.
2. Description of the Related Art
Referring to FIG. 1, a prior art coaxial cable (10) which is used to connect an aerial antenna and a TV includes a central conductor (11) and an outer conductor (13) separated by an insulating material. The central conductor (11) is electrically connected to a central shaft of a plug member (12), and the outer conductor is electrically connected to an annular wall (also an electric conductor) of the plug member. A protective layer (14) is molded on the coaxial cable (10) such that only a section of the plug member (12) by which to connect a TV protrudes from the protective layer (14). A drawback of the above-mentioned coaxial cable is that there is extra expense for making a mold. The protective layer (14) can then only be molded on the coaxial cable (10) and the plug member (12). In addition, the coaxial cable thus produced has poor electromagnetic shielding.
To improve electromagnetic shielding, a new coaxial cable has been invented as shown in FIG. 2. As illustrated, a plastic layer (15) is molded on a section (B) of the coaxial cable. An aluminum foil (16) is manually sleeved on the plastic layer (15) and a plastic protective sleeve (17) is sleeved around the aluminum foil (16). The problem with the above-mentioned coaxial cable is that the process takes a long time, so that thus mass production is slow.
Referring to FIG. 3, a hollow metal tube (18) is substituted for the plastic protective sleeve so as to provide a good electromagnetic shielding. The plug member (12) includes a central shaft (121) and a clamping portion (122) isolated by an insulating layer. The clamping portion (122) of the plug member (12) is inserted through the hollow metal tube (18) to engage the outer conductor of the coaxial wire (10). The clamping portion (122) is pressed inwardly so that the clamping portion (122) engages the outer conductor of the coaxial wire (10). The hollow metal tube is then threaded on the plug member. A drawback of the above-mentioned coaxial cable is that it requires a considerable time to depress the clamping portion inwardly in order to engage the outer conductor (13) of the coaxial wire (10).